Oscillation generation



Nov. 6, 1934. H. o. PETERSON OSG ILLATION GENERATION Filed May 27, 193144 AMPl/F/ Hw- I JECO/VD OETECTaQ u AMPl/FIEQ JMPl/F'IEK Flt 762 Ill All"I vvvyr UIPI/f INVENTOR H.0.PETER on BY W ATTORNEY Patented Nov. 6,I934 UNlTED STA OSOILLATION GENERATION tion of Delaware Application May27, 1931, Serial No. 540,314

9 Claims.

This invention relates to the generation of high frequency oscillationsand is especially directed towards new and useful piezo-electric crystalcontrolled oscillation generators.

It has been proposed, heretofore, to control the frequency ofoscillations generated with a three electrode electron discharge deviceby means of a piezo-electric crystal. In practice I have found that suchtubes have shown extreme reluctance m in producing oscillations, andaccordingly, it is an object of my present invention to overcome thehesitancy of such a system to oscillate. In order to do so I make use oftubes having high interelectrode impedance such as the tetrode or screengrid tubes whereby oscillation generation is facilitated. Moreover, theuse of such tu es or devices insures greater output for a given amountof radio frequency voltage impressed upon the frequency controllingcrystal, thereby offering the advantage that the crystal need not beworked as hard as heretofore required which often times resulted indestruction of the crystal because of its high amplitude of mechanicalvibration.

Another object of my present invention is to provide an oscillator whoseonly resonant fre quency control means shall be a piezo-electric crystalas a result of which frequency stability is enhanced by virtue of thefact that there are no tuned circuits associated with the oscillatorwhich will have an effect upon the crystal frequency.

Still another object of my present invention is to provide anoscillation generator of the regenerative type using a tube having morethan three electrodes wherein feed back shall occur solely through apiezo-electric crystal, the input circuit of the oscillator being madepreferably aperiodic whereby the frequency of oscillations generated inthe output circuit of the oscillator shall substantially always bedetermined by the frequency of only the crystal and may bear, ifdesired, a harmonic relation in frequency to the frequency of operationof the crystal.

Still further objects of my present invention are to providemodifications of the oscillators de- 9 scribed briefly hereinabove, suchas an oscillator having an electron discharge device of the multigridtype, the grid associated with the input circuit being connectedaperiodically to the cathode, the device having resonant meansassociated with another grid; and, broadly resonant means for feedingback energy from the anode to the aperiodic input circuit whereby highfrequency oscillations are sustained in the resonant means associatedwith one of the grids. This resonant means in the grid circuit may, ofcourse, take the form of a tunable circuit and, the feed back may beestablished through a piezo-electric crystal.

As a further modification I provide in accordance with my presentinvention, a tunable circuit associated with the anode and cathode of anelectron discharge device oscillator, the frequency of oscillationsbeing determined by a piezo-electric crystal connected between the gridadjacent the anode, or a grid maintained at a relatively high positivepotential, and the cathode of the electron discharge device oscillator.

As required by law, my present invention is defined with particularityin the appended claims. However, it may best be understood both as toits structural organization and mode of operation by referring to theaccompanying drawing, wherein,

Figure 1 illustrates an improved crystal oscillator, according to mypresent invention, incorporated within a transmitting arrangement,

Figure 2 illustrates another form of oscillator showing its applicationin a superheterodyne receiver, and,

Figure 3 illustrates still another form of my presentinvention.

Turning to Figure 1, the electron discharge device 2 preferably of thescreen grid or tetrode type has an aperiodic input circuit comprisingresistance 4 connected between grid 6 and cathode 8 illustrated as beingof the heater type. Grid 6 is, of course, the normal control gridadjacent the cathode and is suitably polarized by the current flowthrough resistance l. An aperiodic output circuit is connected betweenthe anode 10 and cathode 8 and it comprises a resistance 12 in serieswith a suitable source of anode polarizing potential 14 as well asresistance 16 connected between resistance 12 and the cathode. By theuse of a connection 18, variably tapped to resistance 16, a suitablepositive biasing potential may be applied to the screen grid orelectrode 20 adjacent anode 10. The screen grid is by-passed to groundfor radio frequency currents by the action of suitable condenser 22.

By virtue of screen grid electrode 20 intermediate grid 6 and anode 10there is very little possibility of feed back through the tube, and, inorder to introduce feed back to cause generation at a desired frequencyof oscillation, I connect resonant means preferably in the form of apiezo-electric crystal 24 between the anode 10 and control electrode 6or, in other words, between the aperiodic input and output circuits.

Upon the application of suitable potentials to the various electrodes ofthe tube 2, crystal 24 becomes excited as a result of which currentscorresponding to a natural frequency of the crystal fiow through theinput circuit 4 causing large voltage variations across the outputresistance 12. For frequencies other than a natural frequency of thecrystal, there will be no appreciable current fiow through resistor 4 asa result of which, at other frequencies, there will be no output fromelectron discharge device oscillator 2.

The foregoing oscillator circuit will be found to oscillate readily andin a very stable fashion. It offers the advantage that inasmuch as thereare no tuned circuits associated therewith other than the crystal or itsequivalent, for example, a sharply tuned resonant circuit, any crystalor circuit having a frequency within any desired limits, may be causedto oscillate in the described circuit. Moreover, in the modificationillustrated which is preferred because of the lack of tuned circuits,the frequency of oscillation more closely approaches the true frequencyof the crystal for, as already indicated to some extent, there are notuned circuits acting to influence the frequency of oscillation of thecrystal.

Output energy may be taken from the output circuit of electron dischargedevice 2 through a suitable blocking condenser 26 acting to vary thepotential on a control grid 28 of electron discharge device amplifier30. Control grid 28 is biased by the action of a suitable condenser andresistance arrangement 32. Moreover, tube 30 may be of the screen gridtype having a suitable screen grid 34 polarized by the action of aresistance 36 connecting it to the anode potential lead 38. In the anodelead there is placed a further output resistor 40 which may if desiredbe replaced by a tuned circuit and output energy from resistor 40 may befed in suitable fashion to a further amplifier and modulator tube 42.

By varying the potential on the screen grid 41 of amplifier tube 42,modulation of the high frequency oscillations in the tunable outputcircuit 44 of tube 42 may be accomplished. To vary the potential onscreen'grid 4i and hence modulate the oscillations appearing in outputcircuit 44, a resistor 46 is connected in series with the screen gridbiasing source 48 and, in shunt with the series combination ofresistance 46 and source 48 there is placed an electron discharge device50 supplied with modulating potentials from, for example, a transformer52. As a result, variations in current through resistance 46 will varythe potential on screen grid 41 thereby producing modulation in energyappearing in the output circuit 44.

Of course, any other suitable modulating arrangement may be used suchas, for example, the Heising scheme or, either the plate voltage or gridvoltage of amplifier tube 42 may be varied in a manner similar to thatgiven for screen grid 41. Modulated output energy from tunable circuit44 is then fed to a suitable power amplifier 54 in turn energizing anantenna 56' in order to propagate the modulated energy to a receivingstation.

The electron discharge device oscillator 2 of Figure 2 is identical withthat shown in Figure 1 with the exception that a tunable circuit 58comprising an inductance coil shunted by a variable condenser is placedin series with the polarizing lead 18 for supplying biasing potential tothe electrode 20 adjacent the anode 10. By suitably tuning circuit 58 toa harmonic of crystal 24the amplitude of that harmonic of crystal 24corresponding to the tuning of, tunable; circuit 58 is increased. Thisharmonic energy may be taken directly from tunable circuit 58 bycoupling thereto a coil 60 and the harmonic energy may be amplified by asuitable amplifier 62 and combined in a first detector 64 with amplifiedradio frequency energy initially derived from antenna 66 and amplifiedby a suitable high frequency amplifier 68. The output of the firstdetector 64, which, as is well known in the art, is of an intermediatefrequency, may be further amplified and then detected in a suitabledetector '70 whose output may be supplied to an amplifier and then to atranslating device such as ear phones 72 in order to translate atransmitted signal.

If desired, energy from electron discharge device oscillatcr 2 may betaken, by means of transmission lines '74, from the aperiodic outputcircuit and in particular from output resistor 12. Energy of any desiredfrequency generated by the oscillator may be filtered out by the use ofa suitable filter '76 and utilized in any suitable fashion as founddesirable such as in a receiving systern or, for example, used as thecarrier for some transmitter.

As a further modification of my present invention, utilizing amulti-grid tube for the generation of oscillations, the resonant meansor tuned circuit 58 of Figure 2 may be replaced by a piezoelectriccrystal '78 as shown in Figure 3, and, in order to apply screen gridpotential to the electrode 20 adjacent the anode of plate 10, thecrystal 78 is shunted by a choke coil 80 suitably grounded for highfrequency potentials by the action of condenser 83. Moreover, the plateor anode circuit need not be aperiodic, but between the anode l0 andcathode 8 there may be connected as shown, resonant means in the form ofa tunable circuit 82 from which, as indicated, output energy may betaken and utilized as found desirable.

For best operation of the arrangement shown in Figure 3, the platecircuit 82 should be tuned to substantially the natural frequency of thecrystal '78 or to a frequency slightly higher than a natural frequencyof the crystal 78. The tuning of circuit 82 should, therefore,correspond to the natural fundamental frequency of crystal '78 or, toany desired harmonic thereof.

The circuit shown in Figure 3 is claimed in my divisional application,Serial Number 621,416, filed in the United States Patent Oifice on July8, 1932.

Various modifications of my present invention will, of course, readilysuggest themselves to those skilled in the art. Consequently, my presentinvention is not to be considered limited in any way by themodifications shown but is to be given a scope commensurate to thatindicated by the appended claims.

Having thus described my invention, what I claim is:

1. In a system for generating oscillations, an electron discharge devicehaving an anode, a cathode, a control electrode adjacent said cathode,and another electrode intermediate said control electrode and saidanode, an aperiodic input circuit connected between said controlelectrode and cathode, an aperiodic circuit connected between said anodeand cathode, a tuned circuit having inductance and capacity connectedbetween said electrode intermediate said control electrode and anode,and said cathode, and, a, piezo-electric crystal connectedv between saidanode and said control electrode.

2. In a system, for, generating oscillations, an electron dischargedevice having an anode, a

cathode, a control electrode adjacent said cathode, and anotherelectrode intermediate said control electrode and said anode, anaperiodic input circuit connected between said control electrode andcathode, an aperiodic circuit connected between said anode and cathode,a tuned circuit connected between said electrode, intermediate saidcontrol electrode and anode, and said cathode, and, a connection fromsaid anode to said control electrode for establishing feed back fromsaid anode circuit to said aperiodic input circuit.

3. In a system for generating high frequency oscillations, an electrondischarge device having an anode, a cathode, and a plurality of gridsintermediate said anode and said cathode, an aperiodic high frequencyinput circuit connected between one of said control electrodes and saidcathode, a resonant circuit connected between said other controlelectrode and said cathode, means for maintaining the control electrodeto which said resonant circuit is connected to a potential positiverelative to the control electrode connected to said cathode through saidaperiodic circuit, means for polarizing said anode to a positivepotential, and, means for establishing feed back from said anode to saidaperiodic circuit.

4. In a system for generating high frequency oscillations, an electrondischarge device having an anode, a cathode, and a plurality of gridsintermediate said anode and said cathode, an aperiodic high frequencyinput circuit connected between one of said grids and said cathode, aresonant circuit connected between another grid and said cathode, meansfor maintaining the grid to which said resonant circuit is connected toa potential positive relative to the grid connected to said cathodethrough said aperiodic circuit, means for polarizing said anode to apositive potential, and, a piezo-electric crystal connected between saidanode and said aperiodic input circuit for establishing feed back fromsaid anode to said input circuit.

5. In an oscillation generating system, an electron discharge devicehaving an anode, a cathode, a screen grid adjacent said anode, and acontrol grid adjacent said cathode, a circuit connecting the gridadjacent said cathode and said cathode, a piezo-electric crystalcoupling said anode to said grid adjacent said cathode, a tunablecircuit connected between the grid adjacent said anode and said cathode,and, a circuit connecting said anode and said cathode.

6. In combination, a vacuum tube having an anode, a cathode, a gridadjacent the cathode, and a screen grid, circuits interconnecting saidanode and cathode and said grid adjacent said cathode and said cathode,a piezoelectric crystal connected between said anode and grid adjacentsaid cathode, and a circuit tuned to a harmonic of a natural frequencyof said piezo-electric crystal connected between said screen grid andcathode.

7. Apparatus as claimed in the preceding claim characterized by the factthat the circuit between said grid adjacent said cathode and saidcathode includes a resistor, and by the fact that the circuit connectedbetween said anode and cathode includes a resistor.

8. An oscillation generator comprising a tube having an anode a cathodea control grid and a screen grid, a circuit connected between saidcontrol grid and cathode for subjecting said control grid to a suitableoperating potential with respect to said cathode, a high frequencycircuit connected between said anode and said cathode, a piezo-electriccrystal coupling said anode to said control grid, and, a resonantcircuit connected between said screen grid and cathode, said resonantcircuit being tuned to a harmonic frequency relative to a fundamentalfrequency of said piezo-electric crystal.

9. An oscillation generator comprising a tube having an anode a cathodea control grid and a screen grid, a circuit connected between saidcontrol grid and cathode for subjecting said control grid to a suitableoperating potential with respect to said cathode, a resonant circuitconnected between said screen grid and cathode, a high frequency circuitconnected between said anode and cathode, a piezo-electric crystalcoupling said anode to said control grid, and means for derivingharmonic frequency energy relative to a fundamental frequency of saidpiezo-electric crystal from said circuit connected between said anodeand cathode.

HAROLD OLAF PETERSON.

